JPH07101231B2 - Radar equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device which detects the distance to a target on a plane by utilizing the reflection of radio waves from the target.

[0002]

2. Description of the Related Art A so-called pulse radar that emits a pulsed radio wave while sequentially changing the pointing direction of a radar antenna, reflects the radio wave on the target, and measures the distance to the target by the time until the radio wave arrives again. Is used as one of navigation aids for ships, for example.

In this type of radar device, the level of the reflected signal from a relatively small target located at a long distance varies greatly with each rotation of the antenna, and particularly when the reflected signal becomes weak, it cannot be continuously received every time. Will increase. To alleviate this problem, conventionally, a received signal is stored for a certain period of time and displayed along with an actual image during that time, so that a weak reflected signal can be continuously displayed.

[0004]

However, in addition to the reflected signal from the target object, many unnecessary signals such as rain, snow, white noise or radar interference are superimposed on the received signal, and these unnecessary signals are also stored at the same time. Is displayed.
Therefore, there is a problem that not only the image is difficult to see but also the target object is misread. Further, since the width of the target once written in the memory is maintained, for example, when the target moves relative to the antenna, the target image is enlarged like a tail. was there.

An object of the present invention is to provide a radar device capable of preventing only the above-mentioned unnecessary signal display and reliably detecting only a target object.

[0006]

A radar device of the present invention corresponds to an image memory for storing one screen of image data from a series of radar reception signals, and a radar detection position or a vicinity of the detection position from the image memory. A means for reading the image data, a means for detecting the target from the read image data, a means for narrowing the width of the target with respect to the image data of the detected target, and a value of the image data for the narrowed target. Reduced
And means for Attenuation, means for the image data of the target obtained by the damping to the current image data obtained by the radar reception signal and the summing obtaining a composite image data, means for writing the composite image data to the image memory Consists of.

[0007]

In the radar apparatus of the present invention, the image memory stores one screen of image data from a series of radar image signals, the target is detected from the image data stored in the image memory, and the detected object is detected. The width of the mark is narrowed , and
One, values Ru is attenuated. And to this newly obtained image data, the width is narrowed, and the image data of the target object whose value is attenuated is the summing. The composite image data obtained in this way is written again in the image memory.

[0008] By the above action, since the received signal level is Shi the summing repeatedly against both the image data reduced video sensitivity reception signal level becomes equivalently large increases.
Further, even when the antenna is intermittently received with respect to the rotation, it is continuously displayed. Moreover, since the width of the temporarily written target object in the image memory is paired to the summing the image data of a new target object of this narrowed, even if the target object is relative motion with respect to the antenna The actual size of the target can be accurately obtained without the target image being enlarged like a tail.

On the other hand, unnecessary signals such as rain, snow, white noise or radar interference are randomly generated without being synchronized with the rotation of the antenna, and their width is smaller than that of the reflected signal from the target. Therefore, the unnecessary signal image data is not stored in the image memory and the unnecessary signal is not emphasized.
Therefore, the contrast (sensitivity) between the signal and the unnecessary signal is increased.

[0010]

1 is a block diagram of a radar apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a radar antenna. The transmitting / receiving circuit 2 uses the antenna 1 to transmit and receive pulsed radio waves. The control circuit 3 controls the transmission / reception circuit 2 and the rotation of the radar antenna 1, gives a timing signal to the adder circuit 5 and the image memory 6, and gives distance data R and an antenna angle θ to the image memory 6 as addresses. . The A / D conversion circuit 4 converts the video signal obtained from the transmission / reception circuit 2 into digital data. The adder circuit 5 adds the output data of the level adjusting circuit 13 described later to the digital image data. The image memory 6 stores the new image data obtained by the adding circuit 5 at the R and θ addresses given from the control circuit 3. The display unit 7 reads the stored data of the image memory 6 at a predetermined timing and displays it on the CRT. Further, in the figure, 8 constitutes a width control circuit. The rising edge detection circuit 9 detects the rising edge of the target from the image data sequentially read from the image memory 6 and closes the gate 11. For example, if the image data has 8 levels from 0 to 7,
When the signal level becomes 2 to 7, it is detected as the rising edge of the target. The delay circuit 10 delays a certain number of bits (for example, 1 bit) from the rising edge of the target to enable the gate circuit 11. The gate circuit 11 outputs the output of the rising edge detection circuit and then outputs the output signal of the delay circuit 10. The image data is set to 0 level until a certain time, and the read data of the image memory is output as it is at other times.
Image data with a narrow width that has been bit-cut is output. The level adjusting circuit 13 sets the level of the image data of the target whose width is narrowed at a fixed ratio (for example, 1/2, 2 /).
3) and so on.

The operation of the radar apparatus shown in FIG. 1 will be described with reference to the waveform chart of FIG. In FIG. 2, (a) is the output signal (digital data) of the A / D conversion circuit 4 in FIG. 1, (b) is the output signal of the image memory 6, (c) is the output signal of the width control circuit 8, and (d). Is the output signal of the level adjusting circuit 13, and (e) is the output signal of the adding circuit 5.

In this example, the output signal (a) of the A / D conversion circuit includes a target reflection signal and an unnecessary signal. Figure 1
The rising edge detection circuit 9 shown in FIG. 2 detects the rising edge to of the output signal (b) of the image memory 6. Delay circuit 1
0 opens the gate 11 with a delay of a time T corresponding to a predetermined number of bits. As a result, as shown in (c), a narrow target signal obtained by deleting the rising edge for the predetermined time T is obtained. Then, the level adjusting circuit 13 lowers the level of the entire signal (c) at a constant rate. The addition result of the level-adjusted signal (d) and the radar image signal (a) of this time is written in the image memory 6. At this time, the unnecessary signal is also written into the image memory, but the level of the target reflection signal increases as compared with the unnecessary signal, and the level of the unnecessary signal relatively decreases. Also, make sure that the width of the target signal is narrowed.
Even if the target is moving due to, the signal (d) is
The video signal (a) must not be added within the range.
Yes. Therefore, the radar image signal (a) is only part of it.
Will be emphasized, but still strong enough when viewed
Adjusted. Since the width of the unnecessary signal is sufficiently shorter than the delay time T , the unnecessary signal is not written again in the image memory even if its rising edge is detected.

Even if the time width of the unnecessary signal is relatively wide and the data is once written in the image memory, the unnecessary signal does not appear at the same timing in the next antenna scan, so that the reflected signal from the target object is not present. The level gradually decreases with each antenna scan.

In FIG. 2, the received signal in one sweep is represented as a waveform, but when it is expressed in a plane, it becomes as shown in FIG. In FIG. 3, a hatched target segment indicates a range to be deleted of the targets read from the image memory. In this way, the width of the target can be narrowed by deleting the rising portion of the target by a certain width in the distance direction from the antenna. The data is read out from the image memory at a certain timing earlier, the falling edge of the target is detected, and the width of the target is narrowed by deleting the image data from the falling target by a certain width. Good.

In the above-described embodiment, the image memory is used for reading and writing in the order of the distance R and the antenna azimuth θ, and the width of the target is narrowed when the image memory is read.
A similar operation may be performed by providing a primary memory after the / D conversion. In this case, the reading method of the primary memory and the image memory can be performed in the XY coordinate format, for example, regardless of the polar coordinates. At that time, the width of the target is narrowed in the X-axis direction or the Y-axis direction. FIG. 4 shows an example in which the width of the target is narrowed in the Y-axis direction. The hatched portion in FIG. 4 is a region to be deleted.

In the above embodiment, the same signal processing is always performed regardless of the magnitude of the signal level stored in the image memory and the received signal level at this time. The signal processing method may be switched depending on the signal level. In FIG. 5, the level determination circuit 14 determines the level of the image data of the target read from the image memory 6 and the level of the image data of the current reception signal output from the A / D conversion circuit 4.
When the current (that is, present) received signal level is high, the image data of the current received signal is written in the image memory 6 as it is, and conversely, when the image data level of the image memory 6 is high, as in the previous embodiment. The switching circuit 15 is switched so that the composite image data obtained by adding the image data after the level adjustment to the image data of this time is written in the image memory.

Further, in the above-described embodiment, the width of the target once stored in the image memory is narrowed in the distance direction. However, the image data of the target is temporarily stored in the working memory and the target in the antenna azimuth θ direction. The edge of the target may be detected, and the image data of the target may be deleted by a certain width at the left, right, or both edge portions. FIG. 6 shows an example in which the left side of the target is deleted by a certain angle. The hatched portion in FIG. 6 is a region to be deleted. In addition, the width of the target in the front, rear, left, and right may be narrowed by further combining with the above-described embodiment.

[0018]

According to the present invention, even if a signal having a low received signal level is received a plurality of times by a plurality of antenna scans, continuous image data of a target having a large signal level can be obtained. At that time, even when the target is moving relative to the antenna, the target is not enlarged like a tail, and the target can be obtained in the actual size. On the other hand, unnecessary signals such as rain, snow, white noise or radar interference are not emphasized, and therefore the contrast (sensitivity) between the signal and the unnecessary signal is increased.

[Brief description of drawings]

FIG. 1 is a block diagram of a radar device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a signal of each target of the radar device as a waveform.

FIG. 3 is a schematic view showing how the target device width is shortened by the radar device.

FIG. 4 is a diagram showing how the width of a target is shortened according to another embodiment.

FIG. 5 is a partial block diagram of a radar device according to another embodiment.

FIG. 6 is a diagram showing how the width of a target is shortened in the antenna azimuth direction.

Claims (1)

[Claims] 1. An image memory for storing one screen of image data from a series of radar reception signals, a means for reading image data corresponding to a radar detection position or the vicinity of the detection position from the image memory, and the read image data. From the target, means to narrow the width of the target to the detected image data of the target, and means to attenuate the value of the image data of the narrowed target
And the image data obtained from the radar reception signal this time is reduced to the above.
Means for determining the composite image data to the image data of the target obtained by Attenuation in the summing, the composite image data and means for writing in the image memory radar apparatus.